Heretofore, as a refrigerant for air conditioners, a chlorofluorocarbon such as dichlorofluoromethane (R12) or chlorodifluoromethane (R22) has been used, but such a refrigerant has an ozone layer destruction ability or high global warming potential (GWP). Accordingly, in recent years, it has become common to use tetrafluoroethane (R134a) or the like having a low global warming potential as a substitute.
However, recently, reflecting a higher control on greenhouse gas emission, a substitute having a lower GWP is desired, and as the next generation of refrigerant, use of 2,3,3,3-tetrafluoropropene (R1234yf) is being studied.
As a method for producing 2,3,3,3-tetrafluoropropene, a method is known wherein 2-chloro-1,1,1,2-tetrafluoropropane is used as a raw material, and it is dehydrochlorinated. Further, as a method for producing 2-chloro-1,1,1,2-tetrafluoropropane as the raw material, a method of adding hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene (CH2═CClCF3) (Patent Document 1), or a method of fluorinating chlorine atoms in e.g. fluorotetrachloropropane or dichlorotrifluoropropane (Patent Document 2) is, for example, known.
In the method disclosed in Patent Document 1, going further back to obtain 2-chloro-3,3,3-trifluoropropene, four-step reactions are carried out by using 2,3-dichloropropene as the starting material, and if this 2,3-dichloropropene is taken as the starting material, in order to obtain 2,3,3,3-tetrafluoropropene as the desired material, six-step reactions are required. Thus, the method disclosed in Patent Document 1 had a problem that the number of steps are many, and the production cost tends to be accordingly high. Further, in this method, a step of dehydrochlorination employing an alkali, is essential, and there is also a problem such that a large amount of waste water is generated. Further, also the method disclosed in Patent Document 2 had a problem that it can hardly be carried out on an industrial scale, since many steps are required for the synthesis of the raw material, and a highly toxic chemical substance is used.
As described above, with respect to 2,3,3,3-tetrafluoropropene (R1234yf) which is expected as the next generation of refrigerant, various production methods have been proposed, but a method for producing it efficiently on an industry scale has not yet been known.